| 摘要 |
A non-volatile memory chip enable encoding method allows the storage of both boot code and user application software within a common memory array. The chip enable encoding method further allows a variable number of memory banks to be provided within the non-volatile memory array and allows the system to power-up and execute the boot code before the array configurations are selected by firmware. In one embodiment, a memory controller includes four chip enable output lines for selectively enabling a plurality of ROM banks. One of the ROM banks includes boot code that is executed by the system microprocessor during system boot. If the user requires a ROM array consisting of four ROM banks, a separate chip enable output line is connected to each ROM bank. If the user instead requires a ROM array consisting of, for example, eight ROM banks, an external decoder may be connected to the four chip enable output lines. In this configuration, each output line of the decoder is coupled to a respective bank enable input line of the ROM banks. In either configuration, the chip enable lines are driven in a mutually exclusive relationship during system boot to access the boot code (stored within one of the ROM banks). Subsequently, the encoding of the chip enable signals at the chip enable output lines of the memory controller is dependent upon configuration information stored in a configuration register.
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